The present invention relates to an improved method for conditioning wastepaper preparatory to being recycled, particularly the usual form of wastepaper of wide varieties bundled together and contaminated with various other forms of waste material and compactly bound together in compressed bale form.
More specifically the invention relates to conditioning intact bales of waste material, the form in which most recyclable wastepaper is available, in a manner which lowers the costs of recycling the wastepaper recoverable from the baled waste material and enhances the quality of the cellulosic fibers recovered from the wastepaper from which a variety of end products are produced, such as molded pulp products (e.g., egg packaging cartons, food trays, etc.), loose paper articles such as sacks, paperboard, corrugated paper containers, etc.
Waste cellulosic fibrous material suitable for recycling comes from numerous sources. One such source is post-consumer wastepaper which is paper and/or paperboard which has served its useful life and/or served the purpose for which it was intended and has been discarded by the user. Typical post-consumer wastepaper includes used corrugated containers (OCC), old newspapers and magazines, mixed wastepaper, and paper and/or paperboard that may have received special functional treatments such as wax-dipped containers, curtain coated (wax) boxes and plastic coated stock. In addition, recyclable sources of cellulosic fibrous materials may be obtained from in-plant waste and broke, such as DLK clippings and other waste generated by the die cutting process in the manufacture of corrugated containers or other multi-wall corrugated constructions. The broke (i.e., paper or paperboard that has been rejected during the process of manufacture) may take the form of either "wet broke" (paper taken off the wet press of a paper machine) or "dry broke" (paper which is spoiled in going over the dryers or through the calendar, trimmed off in the rewinding of rolls, trimmed from sheet being prepared for shipping, or rejected for manufacturing defects). Other in-plant waste includes rejected paper, sacks, bags, cartons, boxes or other converted paper products. A portion of the wastepaper often contains contaminants comprising ingredients added to the fibrous materials to impart special properties, such as wax or polymers to reduce the water or moisture sensitivity of the fibrous materials, or substances that may have been applied to the dry fibrous products to effect closure, such as sealing tape, staples, hot melt adhesives or latex for sealing closures. Baled waste material available for recycling usually contains other extraneous waste material of a variety which is entirely foreign to the fibrous cellulosic materials sought to be recovered in the recycling process such as plastic containers and film, household garbage, stones, sand and dirt, metal and fiber bodied containers, wire, etc. Thus, bales containing potentially recyclable paper products may contain portions which either do not comprise cellulosic fibers or comprise cellulosic fibers which are contaminated to such an extent that they require extensive agitating pulping operations for defibration to release the individual fibers from their bonding structure to form a slurry, or are not suitable for producing a satisfactory recyclable fibrous material.
Careful sorting, classification and segregation of the delivered bales of waste material into lots comprising wastepaper having the qualities of being readily recyclable in producing high-quality finished fibrous products would be an onerous and economically impossible task by presently existing means. Therefore, great need exists for methods and apparatus that would condition intact bales of unsegregated, mixed paper materials of which some contain unwanted contaminants so that the mass of baled material could be more economically processed into high grade fibrous pulp suitable for producing high quality finished fibrous products.
The basic conventional process for recycling wastepaper involves introducing masses of waste material containing recyclable wastepaper, either as intact or broken bales of dry waste material into a pulper, sometimes referred to as a digester or slusher. Pulpers are of various forms but basically comprise a housing containing water or some form of aqueous solution and having one or more rotors or agitators which serve to agitate the mixture of waste material and water eventually causing most of the fibrous material of the wastepaper to be defibrated. Defibration results in cellulosic fibers being released from the structure holding them together and accumulating as a water suspension of the fibers or slurry which is floated away and separated from the remaining waste material by various well-known separating means such as screens, etc. This slurry is the source for the recycled fibrous material. Wastepaper recycling processes normally include several pulping devices for sequential pulping of the waste material and an assortment of sorting or screen devices in which the contaminants and pulp are segregated in various stages with some of the larger pulped components being returned to initial stages of pulpers for continued agitation and separation of the fibers into a slurry. Typical of wastepaper recycling processes are the installations described in U.S. Pat. Nos. 4,017,033, 4,387,856 and 4,231,526.
In commerce almost all waste material intended for recycling is provided in the form of bales for ease in handling and storage. The bales vary considerably in size, some measuring 48".times.32".times.39", weighing about 300 to 500 pounds, with other bales weighing between 1,600 to 2,200 pounds or more with typical dimensions of 94".times.44".times.42". The waste recyclable paper product in these bales has a structural form and integrity. Some wastepaper recycling processes involve a mechanically breaking or tearing apart of the dry waste products in the bales prior to introduction into the pulper which damages the fibers of the fibrous waste. In other instances, intact bales are fed into the pulper resulting in the cellulosic fibers of dry baled material being subject to considerable initial damage by the severe agitation in the pulper required to break up and disintegrate the bale, after which the semi-dry fibrous material is further damaged by the pulper agitation before it separates into a wet slurry and becomes water saturated. Means are needed for conditioning the wastepaper fibers contained in baled material so the fibers suffer minimal damage before and during the pulping proces in order that the strength quality of the fibers comprising the slurry product of the recycling process approaches or equals the cleanliness, color and strength of the original virgin fibrous materials or pulps before their initial conversion into paper or board.
Wastepaper comprises cellulosic fibers that are matted and held together by bonds between the fibers. Hence, if the bonds between fibers are weakened, a lesser mechanical force and agitation is required in a pulper to separate the fibers into the slurry of liquid suspension of fibers. It is known that the bonds between fibers in wastepaper and other fibrous waste are weakened by soaking the fibrous waste in water, or preferably in an alkaline solution, which causes the fibers in the fibrous material to swell hence less friction need be applied to the fibrous material for separating it into individual fibers, thus resulting in minimal damage to the fibers in the pulping action. Accordingly, the liquid suspended fibers of the slurry recovered from the recycled wastepaper contained in baled bundles of waste material would be stronger and be less damaged if the contents of the bales were wetted with water or an aqueous solution to establish swelling of the various waste fibrous materials prior to introducing the baled wastepaper into the recycling pulper. The advantages resulting from injecting a sufficient amount of liquid into baled waste material as will saturate and wet the waste fibrous material prior to introduction of the baled material into the recycling pulper is well illustrated by the following examples. These examples indicate the degree of swelling and resultant loss of fiber to fiber bonding of the fibrous material sought to be recovered from the baled waste material that is achieved when the fibrous material has been impregnated either in water or in a solution of water and ammonium hydroxide. Loss of tensile strength of fluid impregnated fibrous material results from the loss of fiber to fiber bonding strength.